linux-kernel - Re: WARNING: kmalloc bug in input_mt_init

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Message-ID: <20180927143537.GB19006@bombadil.infradead.org>
Date:   Thu, 27 Sep 2018 07:35:37 -0700
From:   Matthew Wilcox <willy@...radead.org>
To:     Dmitry Torokhov <dmitry.torokhov@...il.com>
Cc:     Christopher Lameter <cl@...ux.com>,
        Dmitry Vyukov <dvyukov@...gle.com>,
        syzbot+87829a10073277282ad1@...kaller.appspotmail.com,
        Pekka Enberg <penberg@...nel.org>,
        "linux-input@...r.kernel.org" <linux-input@...r.kernel.org>,
        lkml <linux-kernel@...r.kernel.org>,
        Henrik Rydberg <rydberg@...math.org>,
        syzkaller-bugs <syzkaller-bugs@...glegroups.com>,
        Linux-MM <linux-mm@...ck.org>
Subject: Re: WARNING: kmalloc bug in input_mt_init_slots

On Mon, Sep 24, 2018 at 11:41:58AM -0700, Dmitry Torokhov wrote:
> > How large is the allocation? AFACIT nRequests larger than KMALLOC_MAX_SIZE
> > are larger than the maximum allowed by the page allocator. Thus the warning
> > and the NULL return.
> 
> The size in this particular case is being derived from a value passed
> from userspace. Input core does not care about any limits on size of
> memory kmalloc() can support and is perfectly happy with getting NULL
> and telling userspace to go away with their silly requests by returning
> -ENOMEM.
> 
> For the record: I definitely do not want to pre-sanitize size neither in
> uinput nor in input core.

Probably should be using kvzalloc then.